Electroreceptor organs and mechanoreceptor organs located in the bill skin of the platypus are used by the animal to locate prey items, underwater, with eyes and ears closed. The precise manner in how these senses aid the platypus to locate food is not yet known. In this study we provide data on the activity of cortical neurons in the bill representation of SI when stimulated electrically, mechanically, and concurrently. Within the SI bill representation, there are alternating stripes of cortex that represent purely mechanical inputs, and combined electrical and mechanical inputs. Generally, the bimodal units responded more vigorously to electrical stimulation and had very small dynamic ranges, usually saturating within 20 μV cm -1 of threshold. Latencies to electrical or mechanical stimulation were around 25 ms, but were significantly reduced for concurrent stimulation. Combined with the previously reported observation that the receptive fields of bimodal neurons within cortical modules were the same, and that thresholds varied considerably, the observation of limited dynamic range suggests a mechanism for localization of stimuli. A model is developed wherein the relative activation of a module is dependent on its proximity to the source.

Item Type:	Refereed Article
Keywords:	animal experiment; article; brain cell; brain cortex; controlled study; electroreceptor; electrostimulation; feeding behavior; male; mechanical stimulation; mechanoreceptor; monotremate; nonhuman; priority journal; sensory stimulation
Research Division:	Medical and Health Sciences
Research Group:	Neurosciences
Research Field:	Neurology and Neuromuscular Diseases
Objective Division:	Health
Objective Group:	Clinical Health (Organs, Diseases and Abnormal Conditions)
Objective Field:	Nervous System and Disorders
Author:	Calford, MB (Professor Mike Calford)
ID Code:	91282
Year Published:	1996
Web of Science® Times Cited:	21
Deposited By:	Research Division
Deposited On:	2014-05-13
Last Modified:	2014-05-13
Downloads:	0